US10113249B2 - Silicon carbide substrate and method for manufacturing the same - Google Patents

Silicon carbide substrate and method for manufacturing the same Download PDF

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US10113249B2
US10113249B2 US15/520,435 US201515520435A US10113249B2 US 10113249 B2 US10113249 B2 US 10113249B2 US 201515520435 A US201515520435 A US 201515520435A US 10113249 B2 US10113249 B2 US 10113249B2
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cleaning
silicon carbide
carbide substrate
hydrogen peroxide
peroxide water
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US20170306526A1 (en
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Kyoko Okita
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Sumitomo Electric Industries Ltd
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • C30B33/08—Etching
    • C30B33/10—Etching in solutions or melts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
    • B24B37/042—Lapping machines or devices; Accessories designed for working plane surfaces operating processes therefor
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/36—Carbides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02041—Cleaning
    • H01L21/02057—Cleaning during device manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/0445—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising crystalline silicon carbide
    • H01L21/0475—Changing the shape of the semiconductor body, e.g. forming recesses
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/304—Mechanical treatment, e.g. grinding, polishing, cutting
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/30625—With simultaneous mechanical treatment, e.g. mechanico-chemical polishing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/67005—Apparatus not specifically provided for elsewhere
    • H01L21/67011—Apparatus for manufacture or treatment
    • H01L21/67017—Apparatus for fluid treatment
    • H01L21/67028—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like
    • H01L21/6704—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like for wet cleaning or washing
    • H01L21/67057—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like for wet cleaning or washing with the semiconductor substrates being dipped in baths or vessels
    • H01L29/1608—
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D62/00—Semiconductor bodies, or regions thereof, of devices having potential barriers
    • H10D62/80—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials
    • H10D62/83—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials being Group IV materials, e.g. B-doped Si or undoped Ge
    • H10D62/832—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials being Group IV materials, e.g. B-doped Si or undoped Ge being Group IV materials comprising two or more elements, e.g. SiGe
    • H10D62/8325—Silicon carbide
    • H10P50/00—
    • H10P52/00—
    • H10P52/402—
    • H10P70/15—
    • H10P70/20—
    • H10P72/0416—
    • H10P90/12—

Definitions

  • the present disclosure relates to a silicon carbide substrate and a method for manufacturing the same.
  • SiC silicon carbide
  • a silicon carbide substrate sliced from a silicon carbide ingot is polished to smooth a surface thereof, and thereafter the silicon carbide substrate is cleaned.
  • PTD 1 Japanese Patent Laying-Open No. 2010-4073 discloses a technique of cleaning a silicon carbide substrate using an aqueous solution containing sulfuric acid and hydrogen peroxide water.
  • PTD 1 Japanese Patent Laying-Open No. 2010-4073
  • a silicon carbide substrate in accordance with the present disclosure is a silicon carbide substrate having a main surface, the main surface having a surface roughness (Ra) of less than or equal to 0.1 nm, and vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium each having a concentration of less than or equal to 1.0 ⁇ 10 12 atoms/cm 2 in the main surface.
  • Ra surface roughness
  • a method for manufacturing a silicon carbide substrate in accordance with the present disclosure includes steps of preparing a silicon carbide substrate having a main surface, polishing the main surface of the silicon carbide substrate using a polishing agent containing a metal catalyst, and cleaning the silicon carbide substrate after the step of polishing.
  • the step of cleaning includes a step of cleaning the silicon carbide substrate with aqua regia.
  • FIG. 1 is a partial cross sectional view showing a configuration of a silicon carbide substrate in accordance with a first embodiment.
  • FIG. 2 is a flowchart for schematically illustrating a method for manufacturing the silicon carbide substrate in accordance with the first embodiment.
  • FIG. 3 is a schematic view for illustrating one step in the method for manufacturing the silicon carbide substrate in accordance with the first embodiment.
  • FIG. 4 is a schematic configuration diagram of a polishing apparatus used in a polishing step.
  • FIG. 5 is a schematic view for illustrating one step in the method for manufacturing the silicon carbide substrate in accordance with the first embodiment.
  • FIG. 6 is a schematic configuration diagram of a cleaning apparatus used in a cleaning step.
  • FIG. 7 is a flowchart for schematically illustrating a cleaning method in the method for manufacturing the silicon carbide substrate in accordance with the first embodiment.
  • FIG. 8 is a flowchart for schematically illustrating a cleaning method in accordance with a first variation.
  • FIG. 9 is a flowchart for schematically illustrating a cleaning method in accordance with a second variation.
  • CMP Chemical Mechanical Polishing
  • a polishing agent containing a metal catalyst which reforms a surface by a catalytic action to increase oxidizing power of an oxidizing agent is used in order to achieve a good surface roughness at a high polishing speed.
  • the metal catalyst an oxide layer having a hardness lower than that of silicon carbide is formed on the surface of the silicon carbide substrate. Since polishing is promoted by removing the oxide layer by a mechanical force, both a high polishing speed and a good surface roughness can be achieved.
  • the silicon carbide epi layer may locally grow abnormally, and may have a high surface roughness.
  • a silicon carbide substrate in accordance with the present disclosure is a silicon carbide substrate having a main surface, the main surface having a surface roughness (Ra) of less than or equal to 0.1 nm, and vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium each having a concentration of less than or equal to 1.0 ⁇ 10 12 atoms/cm 2 in the main surface.
  • the main surface means a surface on which devices such as a transistor, a diode, and the like are to be formed.
  • the surface roughness (Ra) of the main surface of the silicon carbide substrate is easily set to less than or equal to 0.1 nm by using a polishing agent containing a metal catalyst in the CMP method.
  • the metal catalyst includes at least one metal element selected from the group consisting of vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium, for example. These metal elements have a catalytic action of breaking bonds between atoms arranged in a surface of silicon carbide to cause the surface to be easily oxidized. Thus, an oxide layer having a hardness lower than that of silicon carbide can be suitably formed on the main surface of the silicon carbide substrate. Accordingly, polishing of the silicon carbide substrate can be promoted.
  • a metal derived from the metal catalyst adhering to the main surface of the silicon carbide substrate may remain in the main surface.
  • material molecules of the epi layer may selectively adhere to a portion where the metal remains in an initial stage of epitaxial growth.
  • the epi layer grows abnormally.
  • the epi layer partially grows abnormally, the epi layer has a high surface roughness. Accordingly, in order to reduce the surface roughness of the epi layer, it is required to reduce the metal remaining in the main surface of the silicon carbide substrate.
  • the surface roughness of the epi layer growing on the main surface of the silicon carbide substrate can be reduced.
  • vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium each have a concentration of less than or equal to 2.0 ⁇ 10 11 atoms/cm 2 in the main surface of the silicon carbide substrate.
  • potassium, sodium, calcium, iron, copper, aluminum, and tin in the main surface of the silicon carbide substrate each have a concentration of less than or equal to 1.0 ⁇ 10 10 atoms/cm 2 .
  • the silicon carbide substrate has a diameter of more than or equal to 100 mm.
  • a method for manufacturing a silicon carbide substrate in accordance with the present disclosure includes steps of preparing a silicon carbide substrate having a main surface, polishing the main surface of the silicon carbide substrate using a polishing agent containing a metal catalyst, and cleaning the silicon carbide substrate after the step of polishing.
  • the step of cleaning includes a step of cleaning the silicon carbide substrate with aqua regia.
  • the polishing agent contains at least one metal element selected from the group consisting of vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium, as the metal catalyst.
  • the step of cleaning further includes steps of cleaning the silicon carbide substrate with a sulfuric acid-hydrogen peroxide water mixture, and cleaning the silicon carbide substrate with an ammonia-hydrogen peroxide water mixture after the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture.
  • the step of cleaning with the aqua regia is performed after the step of cleaning with the ammonia-hydrogen peroxide water mixture.
  • the step of cleaning further includes steps of cleaning the silicon carbide substrate with a hydrochloric acid-hydrogen peroxide water mixture after the step of cleaning with the aqua regia, and cleaning the silicon carbide substrate with hydrofluoric acid after the step of cleaning with the hydrochloric acid-hydrogen peroxide water mixture.
  • the metal catalyst and a metal other than the metal catalyst remaining in the main surface of the silicon carbide substrate can be reduced.
  • the “metal other than the metal catalyst” includes, for example, at least one metal selected from the group consisting of potassium, sodium, calcium, iron, copper, aluminum, and tin, for example.
  • a treatment time is set to more than or equal to 15 minutes in each of the steps of cleaning with the sulfuric acid-hydrogen peroxide water mixture, cleaning with the ammonia-hydrogen peroxide water mixture, cleaning with the aqua regia, cleaning with the hydrochloric acid-hydrogen peroxide water mixture, and cleaning with the hydrofluoric acid.
  • the step of cleaning further includes a step of cleaning the silicon carbide substrate with an ammonia-hydrogen peroxide water mixture.
  • the step of cleaning the silicon carbide substrate with the aqua regia is performed after the step of cleaning with the ammonia-hydrogen peroxide water mixture.
  • a treatment time is set to more than or equal to 15 minutes in each of the steps of cleaning with the ammonia-hydrogen peroxide water mixture and cleaning with the aqua regia.
  • the step of cleaning further includes a step of cleaning the silicon carbide substrate with a sulfuric acid-hydrogen peroxide water mixture.
  • the step of cleaning with the aqua regia is performed after the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture.
  • the step of cleaning further includes a step of cleaning the silicon carbide substrate with hydrofluoric acid after the step of cleaning with the aqua regia.
  • a treatment time is set to more than or equal to 15 minutes in each of the steps of cleaning with the sulfuric acid-hydrogen peroxide water mixture, cleaning with the aqua regia, and cleaning with the hydrofluoric acid.
  • the aqua regia in a mixed solution prepared by mixing the aqua regia and ultrapure water has a volume concentration of more than or equal to 50% and less than or equal to 100%.
  • a volume of sulfuric acid contained in the sulfuric acid-hydrogen peroxide water mixture is more than or equal to one time and less than or equal to five times a volume of ultrapure water contained in the sulfuric acid-hydrogen peroxide water mixture
  • a volume of hydrogen peroxide water contained in the sulfuric acid-hydrogen peroxide water mixture is more than or equal to one time and less than or equal to three times the volume of the ultrapure water contained in the sulfuric acid-hydrogen peroxide water mixture.
  • a volume of an aqueous ammonia solution contained in the ammonia-hydrogen peroxide water mixture is more than or equal to one tenth and less than or equal to one time a volume of ultrapure water contained in the ammonia-hydrogen peroxide water mixture
  • a volume of hydrogen peroxide water contained in the ammonia-hydrogen peroxide water mixture is more than or equal to one tenth and less than or equal to one time the volume of the ultrapure water contained in the ammonia-hydrogen peroxide water mixture.
  • the silicon carbide substrate is set to have a temperature of less than or equal to 40° C.
  • FIG. 1 is a partial cross sectional view showing a configuration of a silicon carbide substrate 10 in accordance with the first embodiment.
  • silicon carbide substrate 10 has a main surface 10 A.
  • Silicon carbide substrate 10 is made of a hexagonal silicon carbide single crystal having a polytype of 4H, for example.
  • Silicon carbide substrate 10 contains an n type impurity such as nitrogen, for example.
  • the impurity in silicon carbide substrate 10 has a concentration of, for example, more than or equal to 5.0 ⁇ 10 18 cm ⁇ 3 and less than or equal to 2.0 ⁇ 10 19 cm ⁇ 3 .
  • Silicon carbide substrate 10 has a diameter of, for example, more than or equal to 100 mm (more than or equal to 4 inches), and may have a diameter of more than or equal to 150 mm (6 inches).
  • Main surface 10 A has a surface roughness (Ra) of less than or equal to 0.1 nm.
  • the “surface roughness (Ra)” is a value measured in conformity with JIS B0601.
  • the surface roughness (Ra) can be measured, for example, using an atomic force microscope (AFM).
  • a measurement mode is set to a tapping mode, a measurement region in the tapping mode is set to a square having each side of 10 ⁇ m, a pitch is set to 40 nm, and a measurement depth is set to 1.0 ⁇ m.
  • sampling in the tapping mode is performed under conditions that a scanning speed within the above measurement region is 5 seconds for one cycle, the number of data for each scan line is 512 points, and the number of the scan lines is 512.
  • displacement control for the cantilever is set to 15.50 nm.
  • Main surface 10 A may be, for example, a ⁇ 0001 ⁇ plane, or a surface having a predetermined off angle (for example, an off angle of less than or equal to 10°) with respect to a ⁇ 0001 ⁇ plane.
  • Vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium in main surface 10 A each have a concentration of more than or equal to 1.0 ⁇ 10 6 atoms/cm 2 and less than or equal to 1.0 ⁇ 10 12 atoms/cm 2 . More preferably, potassium, sodium, calcium, iron, copper, aluminum, and tin in main surface 10 A each have a concentration of less than or equal to 1.0 ⁇ 10 10 atoms/cm 2 .
  • the concentration of a metal impurity in main surface 10 A can be measured by ICP-MS (Inductively Coupled Plasma Mass Spectrometry). Specifically, for example, ICP-MS7500 manufactured by Agillent can be used.
  • the method for manufacturing silicon carbide substrate 10 in accordance with the present embodiment includes a preparation step (S 10 ), a polishing step (S 20 ), and a cleaning step (S 30 ).
  • silicon carbide substrate 10 cut out from a single crystal silicon carbide ingot is prepared.
  • silicon carbide substrate 10 in accordance with the present embodiment is made of a hexagonal silicon carbide single crystal having a polytype of 4H, for example, and has a main surface 11 A.
  • polishing apparatus 100 shown in FIG. 4 is used.
  • polishing apparatus 100 for example, a CMP apparatus is used.
  • new main surface 10 A is formed by polishing main surface 11 A.
  • polishing apparatus 100 used in the first embodiment includes a substrate holding portion 101 , a turn table portion 104 , a polishing cloth 102 , and a polishing agent supplying portion 108 .
  • Substrate holding portion 101 includes a pressurizing head rotated by a shaft not shown about a rotation axis C 2 .
  • Turn table portion 104 includes a disk-like portion rotated by a shaft 106 about a rotation axis C 1 . Polishing cloth 102 is fixed on an upper surface of turn table portion 104 . Polishing agent supplying portion 108 for supplying a polishing agent 110 is provided above turn table portion 104 .
  • silicon carbide substrate 10 is attached to a lower surface of the pressurizing head of substrate holding portion 101 , and is arranged such that main surface 11 A faces polishing cloth 102 . Then, the pressurizing head is lowered to apply a predetermined pressure to silicon carbide substrate 10 . Next, substrate holding portion 101 and turn table portion 104 are rotated in the same direction (direction indicated by arrows in FIG. 4 ) while supplying polishing agent 110 from polishing agent supplying portion 108 to polishing cloth 102 . It should be noted that substrate holding portion 101 and turn table portion 104 may be rotated in opposite directions, or one of them may be rotated while the other is secured.
  • Polishing agent 110 used in the polishing step (S 20 ) contains abrasive grains, an oxidizing agent, and a metal catalyst.
  • the abrasive grains are a material which is softer than silicon carbide to reduce a surface roughness and a process-damaged layer.
  • As the abrasive grains for example, colloidal silica, fume silica, alumina, diamond, or the like is used.
  • the oxidizing agent forms an oxide film on main surface 11 A.
  • As the oxidizing agent for example, hydrogen peroxide water, sodium hypochlorite, barium percarbonate, or the like is used.
  • the metal catalyst includes at least one metal element selected from the group consisting of vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium.
  • metal catalyst for example, sodium tungstate, sodium vanadate, sodium molybdate, or the like is used.
  • Polishing agent 110 has a pH of preferably less than or equal to 6 or more than or equal to 9.5, and more preferably less than or equal to 4 or more than or equal to 10.5, to increase a chemical action.
  • the pH of polishing agent 110 can be controlled by adding an inorganic acid such as hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid; an organic acid such as formic acid, acetic acid, oxalic acid, citric acid, malic acid, tartaric acid, succinic acid, phthalic acid, or fumaric acid; an inorganic alkali such as KOH, NaOH, or NH 4 OH; an organic alkali such as choline, amine, or TMAH (tetramethyl ammonium hydroxide); or a salt thereof.
  • an inorganic acid such as hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid
  • an organic acid such as formic acid, acetic acid, oxalic acid
  • Main surface 10 A subjected to the polishing step (S 20 ) has a surface roughness (Ra) of less than or equal to 0.1 nm.
  • Foreign matter such as dust, the polishing agent used in the polishing step (S 20 ), and the like may adhere to main surface 10 A.
  • abrasive grains, an organic substance, a metal, and the like may adhere to main surface 10 A.
  • the metal adhering to main surface 10 A derive from, for example, the metal catalyst contained in the polishing agent, or a surrounding environment.
  • a cleaning apparatus 120 used in the first embodiment includes a cleaning treatment tank 122 , a pump 124 , a filter 126 , and a heater 128 .
  • Cleaning treatment is performed by immersing silicon carbide substrate 10 in cleaning treatment tank 122 filled with a cleaning solution 130 for a certain period of time. At least portions of the foreign matter such as dust, the organic substance, and the metals adhering to immersed main surface 10 A dissolve in cleaning solution 130 and are removed.
  • Cleaning solution 130 is always circulated by pump 124 and is filtered through filter 126 . Further, cleaning solution 130 is maintained at a desired temperature by temperature control performed using heater 128 .
  • the cleaning step (S 30 ) includes a plurality of steps performed in order of cleaning with a sulfuric acid-hydrogen peroxide water mixture (S 31 ), cleaning with an ammonia-hydrogen peroxide water mixture (S 32 ), cleaning with aqua regia (S 33 ), cleaning with a hydrochloric acid-hydrogen peroxide water mixture (S 34 ), and cleaning with hydrofluoric acid (S 35 ), for example.
  • a step of cleaning with ultrapure water may be performed after each step of cleaning is finished, to rinse the cleaning solution and the like remaining in main surface 10 A.
  • ultrapure water for example, water having an electrical resistivity of more than or equal to 15 M ⁇ cm, a total organ carbon (TOC) of less than 100 ppb, and a residual silica of less than 10 ppb can be used. The same applies to ultrapure water used in subsequent steps.
  • TOC total organ carbon
  • an alkali cleaning step may be performed before the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture.
  • abrasive grains such as colloidal silica adhering to main surface 10 A in the polishing step (S 20 ) are removed by TMAH and a surface active agent, for example.
  • the sulfuric acid-hydrogen peroxide water mixture is a solution prepared by mixing sulfuric acid, hydrogen peroxide water, and ultrapure water.
  • sulfuric acid for example, concentrated sulfuric acid having a mass percentage concentration of 98% can be used.
  • hydrogen peroxide water for example, hydrogen peroxide water having a mass percentage concentration of 30% can be used. The same applies to hydrogen peroxide water used in subsequent steps.
  • the volume ratio among the sulfuric acid, the hydrogen peroxide water, and the ultrapure water contained in the sulfuric acid-hydrogen peroxide water mixture is, for example, 1 (sulfuric acid):1 (hydrogen peroxide water):1 (ultrapure water).
  • the volume ratio among the sulfuric acid, the hydrogen peroxide water, and the ultrapure water is 1 (sulfuric acid):1 (hydrogen peroxide water):1 (ultrapure water) to 5 (sulfuric acid):3 (hydrogen peroxide water):1 (ultrapure water).
  • the volume of the sulfuric acid is more than or equal to one time and less than or equal to five times the volume of the ultrapure water
  • the volume of the hydrogen peroxide water is more than or equal to one time and less than or equal to three times the volume of the ultrapure water.
  • the ammonia-hydrogen peroxide water mixture is a solution prepared by mixing an aqueous ammonia solution, hydrogen peroxide water, and ultrapure water.
  • aqueous ammonia solution for example, an aqueous ammonia solution having a mass percentage concentration of 28% can be used.
  • the volume ratio among the aqueous ammonia solution, the hydrogen peroxide water, and the ultrapure water contained in the ammonia-hydrogen peroxide water mixture is, for example, 1 (aqueous ammonia solution):1 (hydrogen peroxide water):10 (ultrapure water).
  • the volume ratio among the aqueous ammonia solution, the hydrogen peroxide water, and the ultrapure water is 1 (aqueous ammonia solution):1 (hydrogen peroxide water):10 (ultrapure water) to 1 (aqueous ammonia solution):1 (hydrogen peroxide water):1 (ultrapure water).
  • the volume of the aqueous ammonia solution is more than or equal to one tenth and less than or equal to one time the volume of the ultrapure water
  • the volume of the hydrogen peroxide water is more than or equal to one tenth and less than or equal to one time the volume of the ultrapure water.
  • the aqua regia is a solution prepared by mixing hydrochloric acid and nitric acid.
  • the “aqua regia” refers to not only a solution prepared by mixing hydrochloric acid and nitric acid, but also a mixed solution of the solution and ultrapure water.
  • the aqua regia a mixed solution of hydrochloric acid and nitric acid
  • the aqua regia has a volume concentration of more than or equal to 50% and less than or equal to 100%.
  • the hydrochloric acid-hydrogen peroxide water mixture is a solution prepared by mixing hydrochloric acid, hydrogen peroxide water, and ultrapure water.
  • hydrochloric acid for example, concentrated hydrochloric acid having a mass percentage concentration of 98% can be used.
  • the volume ratio among the hydrochloric acid, the hydrogen peroxide water, and the ultrapure water contained in the hydrochloric acid-hydrogen peroxide water mixture is, for example, 1 (hydrochloric acid):1 (hydrogen peroxide water):10 (ultrapure water).
  • the volume ratio among the hydrochloric acid, the hydrogen peroxide water, and the ultrapure water is 1 (hydrochloric acid):1 (hydrogen peroxide water):10 (ultrapure water) to 1 (hydrochloric acid):1 (hydrogen peroxide water):5 (ultrapure water).
  • the volume of the hydrochloric acid is more than or equal to one tenth and less than or equal to one fifth the volume of the ultrapure water
  • the volume of the hydrogen peroxide water is more than or equal to one tenth and less than or equal to one fifth the volume of the ultrapure water.
  • a silicon oxide film is removed by the hydrofluoric acid.
  • the hydrofluoric acid in a mixed solution prepared by mixing the hydrofluoric acid and ultrapure water has a concentration of 30%, for example.
  • the hydrofluoric acid in the mixed solution has a concentration of more than or equal to 20% and less than or equal to 50%.
  • the treatment time in each of the above steps (S 31 ) to (S 35 ) is, for example, 30 minutes.
  • the treatment time is preferably more than or equal to 15 minutes, and is more preferably more than or equal to 30 minutes.
  • silicon carbide substrate 10 is at room temperature, for example.
  • silicon carbide substrate 10 is set to have a temperature of less than or equal to 40° C.
  • silicon carbide substrate 10 ( FIG. 1 ) having main surface 10 A with a metal concentration reduced by the cleaning step (S 30 ) is obtained.
  • the cleaning step (S 30 ) in the method for manufacturing silicon carbide substrate 10 in accordance with the present embodiment is not limited to the one described above. Variations of the cleaning step (S 30 ) will be described below.
  • the cleaning step includes a plurality of steps performed in order of cleaning with an ammonia-hydrogen peroxide water mixture (S 32 ) and cleaning with aqua regia (S 33 ), for example.
  • a step of cleaning with ultrapure water may be performed after each step of cleaning is finished.
  • an alkali cleaning step may be performed before the step of cleaning with a sulfuric acid-hydrogen peroxide water mixture.
  • the cleaning step includes a plurality of steps performed in order of cleaning with a sulfuric acid-hydrogen peroxide water mixture (S 31 ), cleaning with an ammonia-hydrogen peroxide water mixture (S 32 ), cleaning with aqua regia (S 33 ), and cleaning with hydrofluoric acid (S 35 ), for example.
  • a step of cleaning with ultrapure water may be performed after each step of cleaning is finished. It should be noted that an alkali cleaning step may be performed before the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture.
  • Table 1 shows the relation between concentrations of metals existing in main surface 10 A and a method of cleaning silicon carbide substrate 10 .
  • Silicon carbide substrate 10 for each of samples 1 to 3 was manufactured by the manufacturing method in accordance with the first embodiment.
  • the cleaning step (S 30 ) for each of samples 1 to 3 will be described below.
  • the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture (S 31 ) was performed.
  • the volume ratio among the sulfuric acid, the hydrogen peroxide water, and the ultrapure water contained in the sulfuric acid-hydrogen peroxide water mixture was 1 (sulfuric acid):1 (hydrogen peroxide water):1 (ultrapure water).
  • the treatment time was 30 minutes, and the sulfuric acid-hydrogen peroxide water mixture was at room temperature.
  • the step of cleaning with the ammonia-hydrogen peroxide water mixture was performed.
  • the volume ratio among the aqueous ammonia solution, the hydrogen peroxide water, and the ultrapure water contained in the ammonia-hydrogen peroxide water mixture was 1 (aqueous ammonia solution):1 (hydrogen peroxide water):10 (ultrapure water).
  • the treatment time was 30 minutes, and the ammonia-hydrogen peroxide water mixture was at room temperature.
  • the step of cleaning with the aqua regia was performed.
  • the volume ratio among the hydrochloric acid, the nitric acid, and the ultrapure water contained in the aqua regia was 3 (hydrochloric acid):1 (nitric acid):0 (ultrapure water).
  • the treatment time was 30 minutes, and the aqua regia was at room temperature.
  • the step of cleaning with the hydrochloric acid-hydrogen peroxide water mixture was performed.
  • the volume ratio among the hydrochloric acid, the hydrogen peroxide water, and the ultrapure water contained in the hydrochloric acid-hydrogen peroxide water mixture was 1 (hydrochloric acid):1 (hydrogen peroxide water):10 (ultrapure water).
  • the treatment time was 30 minutes, and the aqua regia was at room temperature.
  • the step of cleaning with the hydrofluoric acid (S 35 ) was performed.
  • the hydrofluoric acid in a mixed solution prepared by mixing the hydrofluoric acid and ultrapure water had a concentration of 30%.
  • the treatment time was 30 minutes, and the hydrofluoric acid was at room temperature. That is, in the cleaning step (S 30 ) for each of samples 1 to 3, silicon carbide substrate 10 during cleaning was set to have a temperature of less than or equal to 40° C. This cleaning step is entirely performed at room temperature, due to the following reason. Since silicon carbide is chemically inert, it takes a long time to oxidize its surface and perform lift-off.
  • a sulfuric acid-hydrogen peroxide water mixture and a hydrochloric acid-hydrogen peroxide water mixture at a high temperature are used.
  • a sulfuric acid-hydrogen peroxide water mixture and a hydrochloric acid-hydrogen peroxide water mixture at a high temperature are used to clean silicon carbide, the sulfuric acid-hydrogen peroxide water mixture and the hydrochloric acid-hydrogen peroxide water mixture evaporate during cleaning treatment, and thus the cleaning effect is reduced. Accordingly, silicon carbide is preferably cleaned at room temperature.
  • concentrations of metals existing in main surface 10 A were measured.
  • concentrations of vanadium (V), tungsten (W), molybdenum (Mo), platinum (Pt), nickel (Ni), titanium (Ti), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), aluminum (Al), sodium (Na), calcium (Ca), potassium (K), and tin (Sn) were measured.
  • concentrations of vanadium (V) and zinc (Zn) were measured.
  • the concentrations of the metals were measured by ICP-MS.
  • Tables 2 and 3 show measurement results of the concentrations of the metals in main surface 10 A of sample 1.
  • Table 2 shows measurement results of the concentrations of metal catalysts existing in main surface 10 A.
  • the metal concentration indicates a value which is less than or equal to 1.0 ⁇ 10 12 atoms/cm 2 , in main surface 10 A of sample 1.
  • the concentrations of vanadium (V) existing in main surface 10 A of sample 2 and main surface 10 A of sample 3 were 72 ⁇ 10 9 atoms/cm 2 and 16 ⁇ 10 9 atoms/cm 2 , respectively.
  • Table 3 shows measurement results of the concentrations of metals existing in main surface 10 A other than the metal catalysts. It should be noted that “ND” in Table 3 indicates that the concentration was undetectable because it was lower than a detection lower limit value (1 ⁇ 10 7 atoms/cm 2 ).
  • iron (Fe), copper (Cu), zinc (Zn), aluminum (Al), sodium (Na), calcium (Ca), potassium (K), and tin (Sn) were confirmed as the metals other than the metal catalysts, in main surface 10 A of sample 1. However, it was confirmed that these metals in main surface 10 A of sample 1 each had a concentration lower than 1 ⁇ 10 11 atoms/cm 2 .
  • concentrations of zinc (Zn) existing in main surface 10 A of sample 2 and main surface 10 A of sample 3 were 16 ⁇ 10 9 atoms/cm 2 and 21 ⁇ 10 9 atoms/cm 2 , respectively.
  • 10 silicon carbide substrate; 10 A: main surface; 11 A: main surface; 20 : epitaxial layer; 30 : metal impurity; 100 : polishing apparatus; 101 : substrate holding portion; 102 : polishing cloth; 104 : turn table portion; 106 : shaft; 108 : polishing agent supplying portion; 110 : polishing agent; 120 : cleaning apparatus; 122 : cleaning treatment tank; 124 : pump; 126 : filter; 128 : heater.

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Abstract

A method for manufacturing a silicon carbide substrate includes steps of preparing a silicon carbide substrate having a main surface, polishing the main surface of the silicon carbide substrate using a polishing agent containing a metal catalyst, and cleaning the silicon carbide substrate after the step of polishing. The step of cleaning includes a step of cleaning the silicon carbide substrate with aqua regia.

Description

TECHNICAL FIELD
The present disclosure relates to a silicon carbide substrate and a method for manufacturing the same.
BACKGROUND ART
In recent years, in order to achieve high breakdown voltage, low loss, and the like in a semiconductor device, silicon carbide (SiC) has begun to be adopted as a material constituting the semiconductor device.
In the process of manufacturing a silicon carbide substrate, a silicon carbide substrate sliced from a silicon carbide ingot is polished to smooth a surface thereof, and thereafter the silicon carbide substrate is cleaned. For example, PTD 1 (Japanese Patent Laying-Open No. 2010-4073) discloses a technique of cleaning a silicon carbide substrate using an aqueous solution containing sulfuric acid and hydrogen peroxide water.
CITATION LIST Patent Document
PTD 1: Japanese Patent Laying-Open No. 2010-4073
SUMMARY OF INVENTION
A silicon carbide substrate in accordance with the present disclosure is a silicon carbide substrate having a main surface, the main surface having a surface roughness (Ra) of less than or equal to 0.1 nm, and vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium each having a concentration of less than or equal to 1.0×1012 atoms/cm2 in the main surface.
A method for manufacturing a silicon carbide substrate in accordance with the present disclosure includes steps of preparing a silicon carbide substrate having a main surface, polishing the main surface of the silicon carbide substrate using a polishing agent containing a metal catalyst, and cleaning the silicon carbide substrate after the step of polishing. The step of cleaning includes a step of cleaning the silicon carbide substrate with aqua regia.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a partial cross sectional view showing a configuration of a silicon carbide substrate in accordance with a first embodiment.
FIG. 2 is a flowchart for schematically illustrating a method for manufacturing the silicon carbide substrate in accordance with the first embodiment.
FIG. 3 is a schematic view for illustrating one step in the method for manufacturing the silicon carbide substrate in accordance with the first embodiment.
FIG. 4 is a schematic configuration diagram of a polishing apparatus used in a polishing step.
FIG. 5 is a schematic view for illustrating one step in the method for manufacturing the silicon carbide substrate in accordance with the first embodiment.
FIG. 6 is a schematic configuration diagram of a cleaning apparatus used in a cleaning step.
FIG. 7 is a flowchart for schematically illustrating a cleaning method in the method for manufacturing the silicon carbide substrate in accordance with the first embodiment.
FIG. 8 is a flowchart for schematically illustrating a cleaning method in accordance with a first variation.
FIG. 9 is a flowchart for schematically illustrating a cleaning method in accordance with a second variation.
 DESCRIPTION OF EMBODIMENTS Description of Embodiment
To polish a silicon carbide substrate, for example. a chemical mechanical polishing method called CMP (Chemical Mechanical Polishing) method is adopted. In the CMP method, for example, a polishing agent containing a metal catalyst which reforms a surface by a catalytic action to increase oxidizing power of an oxidizing agent is used in order to achieve a good surface roughness at a high polishing speed. By the metal catalyst, an oxide layer having a hardness lower than that of silicon carbide is formed on the surface of the silicon carbide substrate. Since polishing is promoted by removing the oxide layer by a mechanical force, both a high polishing speed and a good surface roughness can be achieved.
However, when a silicon carbide substrate is polished using a polishing agent containing a metal catalyst and thereafter a silicon carbide epitaxial layer (hereinafter also referred to as an epi layer) is grown on the silicon carbide substrate, the silicon carbide epi layer may locally grow abnormally, and may have a high surface roughness.
First, aspects of the present disclosure will be described in list form.
(1) A silicon carbide substrate in accordance with the present disclosure is a silicon carbide substrate having a main surface, the main surface having a surface roughness (Ra) of less than or equal to 0.1 nm, and vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium each having a concentration of less than or equal to 1.0×1012 atoms/cm2 in the main surface. Here, the main surface means a surface on which devices such as a transistor, a diode, and the like are to be formed.
The surface roughness (Ra) of the main surface of the silicon carbide substrate is easily set to less than or equal to 0.1 nm by using a polishing agent containing a metal catalyst in the CMP method.
The metal catalyst includes at least one metal element selected from the group consisting of vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium, for example. These metal elements have a catalytic action of breaking bonds between atoms arranged in a surface of silicon carbide to cause the surface to be easily oxidized. Thus, an oxide layer having a hardness lower than that of silicon carbide can be suitably formed on the main surface of the silicon carbide substrate. Accordingly, polishing of the silicon carbide substrate can be promoted.
However, even when the silicon carbide substrate is cleaned after being polished using the polishing agent containing the metal catalyst described above, a metal derived from the metal catalyst adhering to the main surface of the silicon carbide substrate may remain in the main surface. When an epi layer is grown on the silicon carbide substrate having the metal remaining in the main surface, material molecules of the epi layer may selectively adhere to a portion where the metal remains in an initial stage of epitaxial growth. As a result, the epi layer grows abnormally. When the epi layer partially grows abnormally, the epi layer has a high surface roughness. Accordingly, in order to reduce the surface roughness of the epi layer, it is required to reduce the metal remaining in the main surface of the silicon carbide substrate.
In the silicon carbide substrate described above, the surface roughness of the epi layer growing on the main surface of the silicon carbide substrate can be reduced.
(2) Preferably, in the silicon carbide substrate described above, vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium each have a concentration of less than or equal to 2.0×1011 atoms/cm2 in the main surface of the silicon carbide substrate.
(3) Preferably, in the silicon carbide substrate described above in (1) or (2), potassium, sodium, calcium, iron, copper, aluminum, and tin in the main surface of the silicon carbide substrate each have a concentration of less than or equal to 1.0×1010 atoms/cm2.
(4) Preferably, in the silicon carbide substrate described above in any of (1) to (3), the silicon carbide substrate has a diameter of more than or equal to 100 mm.
(5) A method for manufacturing a silicon carbide substrate in accordance with the present disclosure includes steps of preparing a silicon carbide substrate having a main surface, polishing the main surface of the silicon carbide substrate using a polishing agent containing a metal catalyst, and cleaning the silicon carbide substrate after the step of polishing. The step of cleaning includes a step of cleaning the silicon carbide substrate with aqua regia. By cleaning the silicon carbide substrate with the aqua regia after polishing it, the metal catalyst remaining in the main surface, which is a polished surface, of the silicon carbide substrate can be removed. Therefore, the surface roughness of the epi layer formed on the main surface can be reduced.
(6) Preferably, in the method for manufacturing the silicon carbide substrate described above, in the step of polishing, the polishing agent contains at least one metal element selected from the group consisting of vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium, as the metal catalyst.
(7) Preferably, in the method for manufacturing the silicon carbide substrate described above in (5) or (6), the step of cleaning further includes steps of cleaning the silicon carbide substrate with a sulfuric acid-hydrogen peroxide water mixture, and cleaning the silicon carbide substrate with an ammonia-hydrogen peroxide water mixture after the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture. The step of cleaning with the aqua regia is performed after the step of cleaning with the ammonia-hydrogen peroxide water mixture. The step of cleaning further includes steps of cleaning the silicon carbide substrate with a hydrochloric acid-hydrogen peroxide water mixture after the step of cleaning with the aqua regia, and cleaning the silicon carbide substrate with hydrofluoric acid after the step of cleaning with the hydrochloric acid-hydrogen peroxide water mixture. Thereby, the metal catalyst and a metal other than the metal catalyst remaining in the main surface of the silicon carbide substrate can be reduced. The “metal other than the metal catalyst” includes, for example, at least one metal selected from the group consisting of potassium, sodium, calcium, iron, copper, aluminum, and tin, for example.
(8) Preferably, in the method for manufacturing the silicon carbide substrate described above in (7), a treatment time is set to more than or equal to 15 minutes in each of the steps of cleaning with the sulfuric acid-hydrogen peroxide water mixture, cleaning with the ammonia-hydrogen peroxide water mixture, cleaning with the aqua regia, cleaning with the hydrochloric acid-hydrogen peroxide water mixture, and cleaning with the hydrofluoric acid.
(9) Preferably, in the method for manufacturing the silicon carbide substrate described above in (5) or (6), the step of cleaning further includes a step of cleaning the silicon carbide substrate with an ammonia-hydrogen peroxide water mixture. The step of cleaning the silicon carbide substrate with the aqua regia is performed after the step of cleaning with the ammonia-hydrogen peroxide water mixture. Thereby, an organic substance adhering to the main surface of the silicon carbide substrate can be reduced, and the metal catalyst and the metal other than the metal catalyst remaining in the main surface of the silicon carbide substrate can be reduced.
(10) Preferably, in the method for manufacturing the silicon carbide substrate described above in (9), a treatment time is set to more than or equal to 15 minutes in each of the steps of cleaning with the ammonia-hydrogen peroxide water mixture and cleaning with the aqua regia.
(11) Preferably, in the method for manufacturing the silicon carbide substrate described above in (5) or (6), the step of cleaning further includes a step of cleaning the silicon carbide substrate with a sulfuric acid-hydrogen peroxide water mixture. The step of cleaning with the aqua regia is performed after the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture. The step of cleaning further includes a step of cleaning the silicon carbide substrate with hydrofluoric acid after the step of cleaning with the aqua regia.
(12) In the method for manufacturing the silicon carbide substrate described above in (11), a treatment time is set to more than or equal to 15 minutes in each of the steps of cleaning with the sulfuric acid-hydrogen peroxide water mixture, cleaning with the aqua regia, and cleaning with the hydrofluoric acid.
(13) Preferably, in the method for manufacturing the silicon carbide substrate described above in any of (5) to (12), in the step of cleaning with the aqua regia, the aqua regia in a mixed solution prepared by mixing the aqua regia and ultrapure water has a volume concentration of more than or equal to 50% and less than or equal to 100%.
(14) Preferably, in the method for manufacturing the silicon carbide substrate described above in any of (7), (8), (11), and (12), in the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture, a volume of sulfuric acid contained in the sulfuric acid-hydrogen peroxide water mixture is more than or equal to one time and less than or equal to five times a volume of ultrapure water contained in the sulfuric acid-hydrogen peroxide water mixture, and a volume of hydrogen peroxide water contained in the sulfuric acid-hydrogen peroxide water mixture is more than or equal to one time and less than or equal to three times the volume of the ultrapure water contained in the sulfuric acid-hydrogen peroxide water mixture.
(15) Preferably, in the method for manufacturing the silicon carbide substrate described above in any of (7) to (10), in the step of cleaning with the ammonia-hydrogen peroxide water mixture, a volume of an aqueous ammonia solution contained in the ammonia-hydrogen peroxide water mixture is more than or equal to one tenth and less than or equal to one time a volume of ultrapure water contained in the ammonia-hydrogen peroxide water mixture, and a volume of hydrogen peroxide water contained in the ammonia-hydrogen peroxide water mixture is more than or equal to one tenth and less than or equal to one time the volume of the ultrapure water contained in the ammonia-hydrogen peroxide water mixture.
(16) Preferably, in the method for manufacturing the silicon carbide substrate described above in any of (5) to (15), in the step of cleaning, the silicon carbide substrate is set to have a temperature of less than or equal to 40° C.
Details of Embodiment
Hereinafter, a specific example of an embodiment of the present disclosure will be described with reference to the drawings. It should be noted that identical or corresponding parts in the following drawings will be designated by the same reference numerals, and the description thereof will not be repeated. Further, in the present specification, an individual plane is represented by ( ), and a group plane is represented by { }. In addition, a negative index is supposed to be crystallographically indicated by putting “−” (bar) above a numeral, but is indicated by putting the negative sign before the numeral in the present specification.
First Embodiment
<Configuration of Silicon Carbide Substrate>
First, a configuration of a silicon carbide substrate in accordance with a first embodiment will be described. FIG. 1 is a partial cross sectional view showing a configuration of a silicon carbide substrate 10 in accordance with the first embodiment.
As shown in FIG. 1, silicon carbide substrate 10 has a main surface 10A. Silicon carbide substrate 10 is made of a hexagonal silicon carbide single crystal having a polytype of 4H, for example. Silicon carbide substrate 10 contains an n type impurity such as nitrogen, for example. The impurity in silicon carbide substrate 10 has a concentration of, for example, more than or equal to 5.0×1018 cm−3 and less than or equal to 2.0×1019 cm−3. Silicon carbide substrate 10 has a diameter of, for example, more than or equal to 100 mm (more than or equal to 4 inches), and may have a diameter of more than or equal to 150 mm (6 inches).
Main surface 10A has a surface roughness (Ra) of less than or equal to 0.1 nm. The “surface roughness (Ra)” is a value measured in conformity with JIS B0601. The surface roughness (Ra) can be measured, for example, using an atomic force microscope (AFM).
As an AFM, for example, “Dimension 300” manufactured by Veeco can be used. In addition, as a cantilever (probe) of the above AFM, for example, a model “NCHV-10V” manufactured by Bruker can be used. As conditions for measurement with the AFM, as one example, a measurement mode is set to a tapping mode, a measurement region in the tapping mode is set to a square having each side of 10 μm, a pitch is set to 40 nm, and a measurement depth is set to 1.0 μm. In addition, sampling in the tapping mode is performed under conditions that a scanning speed within the above measurement region is 5 seconds for one cycle, the number of data for each scan line is 512 points, and the number of the scan lines is 512. Further, displacement control for the cantilever is set to 15.50 nm.
Main surface 10A may be, for example, a {0001} plane, or a surface having a predetermined off angle (for example, an off angle of less than or equal to 10°) with respect to a {0001} plane.
Vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium in main surface 10A each have a concentration of more than or equal to 1.0×106 atoms/cm2 and less than or equal to 1.0×1012 atoms/cm2. More preferably, potassium, sodium, calcium, iron, copper, aluminum, and tin in main surface 10A each have a concentration of less than or equal to 1.0×1010 atoms/cm2. The concentration of a metal impurity in main surface 10A can be measured by ICP-MS (Inductively Coupled Plasma Mass Spectrometry). Specifically, for example, ICP-MS7500 manufactured by Agillent can be used.
<Method for Manufacturing Silicon Carbide Substrate>
A method for manufacturing silicon carbide substrate 10 in accordance with the first embodiment will be described. As shown in FIG. 2, the method for manufacturing silicon carbide substrate 10 in accordance with the present embodiment includes a preparation step (S10), a polishing step (S20), and a cleaning step (S30).
In the preparation step (S10), silicon carbide substrate 10 cut out from a single crystal silicon carbide ingot is prepared. As shown in FIG. 3, silicon carbide substrate 10 in accordance with the present embodiment is made of a hexagonal silicon carbide single crystal having a polytype of 4H, for example, and has a main surface 11A.
In a grinding step (S20), for example, a polishing apparatus 100 shown in FIG. 4 is used. As polishing apparatus 100, for example, a CMP apparatus is used. In the polishing step (S20), as shown in FIG. 5, new main surface 10A is formed by polishing main surface 11A. As shown in FIG. 4, polishing apparatus 100 used in the first embodiment includes a substrate holding portion 101, a turn table portion 104, a polishing cloth 102, and a polishing agent supplying portion 108. Substrate holding portion 101 includes a pressurizing head rotated by a shaft not shown about a rotation axis C2. Turn table portion 104 includes a disk-like portion rotated by a shaft 106 about a rotation axis C1. Polishing cloth 102 is fixed on an upper surface of turn table portion 104. Polishing agent supplying portion 108 for supplying a polishing agent 110 is provided above turn table portion 104.
When the polishing step (S20) is performed, silicon carbide substrate 10 is attached to a lower surface of the pressurizing head of substrate holding portion 101, and is arranged such that main surface 11A faces polishing cloth 102. Then, the pressurizing head is lowered to apply a predetermined pressure to silicon carbide substrate 10. Next, substrate holding portion 101 and turn table portion 104 are rotated in the same direction (direction indicated by arrows in FIG. 4) while supplying polishing agent 110 from polishing agent supplying portion 108 to polishing cloth 102. It should be noted that substrate holding portion 101 and turn table portion 104 may be rotated in opposite directions, or one of them may be rotated while the other is secured.
Polishing agent 110 used in the polishing step (S20) contains abrasive grains, an oxidizing agent, and a metal catalyst. The abrasive grains are a material which is softer than silicon carbide to reduce a surface roughness and a process-damaged layer. As the abrasive grains, for example, colloidal silica, fume silica, alumina, diamond, or the like is used. The oxidizing agent forms an oxide film on main surface 11A. As the oxidizing agent, for example, hydrogen peroxide water, sodium hypochlorite, barium percarbonate, or the like is used.
The metal catalyst includes at least one metal element selected from the group consisting of vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium. As the metal catalyst, for example, sodium tungstate, sodium vanadate, sodium molybdate, or the like is used.
Polishing agent 110 has a pH of preferably less than or equal to 6 or more than or equal to 9.5, and more preferably less than or equal to 4 or more than or equal to 10.5, to increase a chemical action. The pH of polishing agent 110 can be controlled by adding an inorganic acid such as hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid; an organic acid such as formic acid, acetic acid, oxalic acid, citric acid, malic acid, tartaric acid, succinic acid, phthalic acid, or fumaric acid; an inorganic alkali such as KOH, NaOH, or NH4OH; an organic alkali such as choline, amine, or TMAH (tetramethyl ammonium hydroxide); or a salt thereof.
Main surface 10A subjected to the polishing step (S20) has a surface roughness (Ra) of less than or equal to 0.1 nm. Foreign matter such as dust, the polishing agent used in the polishing step (S20), and the like may adhere to main surface 10A. Specifically, abrasive grains, an organic substance, a metal, and the like may adhere to main surface 10A. The metal adhering to main surface 10A derive from, for example, the metal catalyst contained in the polishing agent, or a surrounding environment.
Next, the cleaning step (S30: FIG. 2) is performed. As shown in FIG. 6, a cleaning apparatus 120 used in the first embodiment includes a cleaning treatment tank 122, a pump 124, a filter 126, and a heater 128. Cleaning treatment is performed by immersing silicon carbide substrate 10 in cleaning treatment tank 122 filled with a cleaning solution 130 for a certain period of time. At least portions of the foreign matter such as dust, the organic substance, and the metals adhering to immersed main surface 10A dissolve in cleaning solution 130 and are removed. Cleaning solution 130 is always circulated by pump 124 and is filtered through filter 126. Further, cleaning solution 130 is maintained at a desired temperature by temperature control performed using heater 128.
As shown in FIG. 7, the cleaning step (S30) includes a plurality of steps performed in order of cleaning with a sulfuric acid-hydrogen peroxide water mixture (S31), cleaning with an ammonia-hydrogen peroxide water mixture (S32), cleaning with aqua regia (S33), cleaning with a hydrochloric acid-hydrogen peroxide water mixture (S34), and cleaning with hydrofluoric acid (S35), for example. A step of cleaning with ultrapure water may be performed after each step of cleaning is finished, to rinse the cleaning solution and the like remaining in main surface 10A. As the ultrapure water, for example, water having an electrical resistivity of more than or equal to 15 MΩ·cm, a total organ carbon (TOC) of less than 100 ppb, and a residual silica of less than 10 ppb can be used. The same applies to ultrapure water used in subsequent steps.
It should be noted that an alkali cleaning step may be performed before the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture. In the alkali cleaning step, abrasive grains such as colloidal silica adhering to main surface 10A in the polishing step (S20) are removed by TMAH and a surface active agent, for example.
In the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture (S31), the organic substance and the like adhering to main surface 10A are removed by the sulfuric acid-hydrogen peroxide water mixture. The sulfuric acid-hydrogen peroxide water mixture is a solution prepared by mixing sulfuric acid, hydrogen peroxide water, and ultrapure water. As the sulfuric acid, for example, concentrated sulfuric acid having a mass percentage concentration of 98% can be used. As the hydrogen peroxide water, for example, hydrogen peroxide water having a mass percentage concentration of 30% can be used. The same applies to hydrogen peroxide water used in subsequent steps.
The volume ratio among the sulfuric acid, the hydrogen peroxide water, and the ultrapure water contained in the sulfuric acid-hydrogen peroxide water mixture is, for example, 1 (sulfuric acid):1 (hydrogen peroxide water):1 (ultrapure water). Preferably, the volume ratio among the sulfuric acid, the hydrogen peroxide water, and the ultrapure water is 1 (sulfuric acid):1 (hydrogen peroxide water):1 (ultrapure water) to 5 (sulfuric acid):3 (hydrogen peroxide water):1 (ultrapure water). In other words, the volume of the sulfuric acid is more than or equal to one time and less than or equal to five times the volume of the ultrapure water, and the volume of the hydrogen peroxide water is more than or equal to one time and less than or equal to three times the volume of the ultrapure water.
Next, in the step of cleaning with the ammonia-hydrogen peroxide water mixture (S32), the organic substance adhering to main surface 10A is removed by the ammonia-hydrogen peroxide water mixture. The ammonia-hydrogen peroxide water mixture is a solution prepared by mixing an aqueous ammonia solution, hydrogen peroxide water, and ultrapure water. As the aqueous ammonia solution, for example, an aqueous ammonia solution having a mass percentage concentration of 28% can be used.
The volume ratio among the aqueous ammonia solution, the hydrogen peroxide water, and the ultrapure water contained in the ammonia-hydrogen peroxide water mixture is, for example, 1 (aqueous ammonia solution):1 (hydrogen peroxide water):10 (ultrapure water). Preferably, the volume ratio among the aqueous ammonia solution, the hydrogen peroxide water, and the ultrapure water is 1 (aqueous ammonia solution):1 (hydrogen peroxide water):10 (ultrapure water) to 1 (aqueous ammonia solution):1 (hydrogen peroxide water):1 (ultrapure water). In other words, the volume of the aqueous ammonia solution is more than or equal to one tenth and less than or equal to one time the volume of the ultrapure water, and the volume of the hydrogen peroxide water is more than or equal to one tenth and less than or equal to one time the volume of the ultrapure water.
Next, in the step of cleaning with the aqua regia (S33), at least a portion of the metal derived from the metal catalyst remaining in main surface 10A is removed by the aqua regia. That is, the metals remaining in main surface 10A are reduced. The aqua regia is a solution prepared by mixing hydrochloric acid and nitric acid. In the present specification, the “aqua regia” refers to not only a solution prepared by mixing hydrochloric acid and nitric acid, but also a mixed solution of the solution and ultrapure water. In the first embodiment, the volume ratio among the hydrochloric acid, the nitric acid, and the ultrapure water contained in the aqua regia is, for example, 3 (hydrochloric acid):1 (nitric acid):0 (ultrapure water). Preferably, the volume ratio among the hydrochloric acid, the nitric acid, and the ultrapure water is 3 (hydrochloric acid):1 (nitric acid):0 (ultrapure water) to 3 (hydrochloric acid):1 (nitric acid):2 (ultrapure water). Preferably, in a mixed solution prepared by mixing aqua regia (a mixed solution of hydrochloric acid and nitric acid) and ultrapure water, the aqua regia has a volume concentration of more than or equal to 50% and less than or equal to 100%.
Next, in the step of cleaning with the hydrochloric acid-hydrogen peroxide water mixture (S34), at least a portion of the metal remaining in main surface 10A other than the metal derived from the metal catalyst is removed by the hydrochloric acid-hydrogen peroxide water mixture. The hydrochloric acid-hydrogen peroxide water mixture is a solution prepared by mixing hydrochloric acid, hydrogen peroxide water, and ultrapure water. As the hydrochloric acid, for example, concentrated hydrochloric acid having a mass percentage concentration of 98% can be used.
The volume ratio among the hydrochloric acid, the hydrogen peroxide water, and the ultrapure water contained in the hydrochloric acid-hydrogen peroxide water mixture is, for example, 1 (hydrochloric acid):1 (hydrogen peroxide water):10 (ultrapure water). Preferably, the volume ratio among the hydrochloric acid, the hydrogen peroxide water, and the ultrapure water is 1 (hydrochloric acid):1 (hydrogen peroxide water):10 (ultrapure water) to 1 (hydrochloric acid):1 (hydrogen peroxide water):5 (ultrapure water). In other words, the volume of the hydrochloric acid is more than or equal to one tenth and less than or equal to one fifth the volume of the ultrapure water, and the volume of the hydrogen peroxide water is more than or equal to one tenth and less than or equal to one fifth the volume of the ultrapure water.
Next, in the step of cleaning with the hydrofluoric acid (S35), a silicon oxide film is removed by the hydrofluoric acid. The hydrofluoric acid in a mixed solution prepared by mixing the hydrofluoric acid and ultrapure water has a concentration of 30%, for example. Preferably, the hydrofluoric acid in the mixed solution has a concentration of more than or equal to 20% and less than or equal to 50%.
The treatment time in each of the above steps (S31) to (S35) is, for example, 30 minutes. The treatment time is preferably more than or equal to 15 minutes, and is more preferably more than or equal to 30 minutes.
In each of the above steps (S31) to (S35), silicon carbide substrate 10 is at room temperature, for example. Preferably, in each step, silicon carbide substrate 10 is set to have a temperature of less than or equal to 40° C.
As described above, silicon carbide substrate 10 (FIG. 1) having main surface 10A with a metal concentration reduced by the cleaning step (S30) is obtained.
The cleaning step (S30) in the method for manufacturing silicon carbide substrate 10 in accordance with the present embodiment is not limited to the one described above. Variations of the cleaning step (S30) will be described below.
(First Variation)
As shown in FIG. 8, the cleaning step includes a plurality of steps performed in order of cleaning with an ammonia-hydrogen peroxide water mixture (S32) and cleaning with aqua regia (S33), for example. A step of cleaning with ultrapure water may be performed after each step of cleaning is finished. It should be noted that an alkali cleaning step may be performed before the step of cleaning with a sulfuric acid-hydrogen peroxide water mixture.
(Second Variation)
As shown in FIG. 9, the cleaning step includes a plurality of steps performed in order of cleaning with a sulfuric acid-hydrogen peroxide water mixture (S31), cleaning with an ammonia-hydrogen peroxide water mixture (S32), cleaning with aqua regia (S33), and cleaning with hydrofluoric acid (S35), for example. A step of cleaning with ultrapure water may be performed after each step of cleaning is finished. It should be noted that an alkali cleaning step may be performed before the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture.
EXAMPLE
Table 1 shows the relation between concentrations of metals existing in main surface 10A and a method of cleaning silicon carbide substrate 10.
TABLE 1
Samples 1 to 3
Cleaning Sulfuric Acid-Hydrogen Peroxide Water Mixture
Solution (1:1:1)
(Treatment Room Temperature/30 Minutes
Temperature Ammonia-Hydrogen Peroxide Water Mixture
Treatment (1:1:10)
Time) Room Temperature/30 Minutes
Aqua Regia
(3:1)
Room Temperature/30 Minutes
Hydrochloric Acid-Hydrogen Peroxide Water Mixture
(1:1:10)
Room Temperature/30 Minutes
Hydrofluoric Acid
(30%)
Room Temperature/30 Minutes
Silicon carbide substrate 10 for each of samples 1 to 3 was manufactured by the manufacturing method in accordance with the first embodiment.
Details of the cleaning step (S30) for each of samples 1 to 3 will be described below. First, the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture (S31) was performed. The volume ratio among the sulfuric acid, the hydrogen peroxide water, and the ultrapure water contained in the sulfuric acid-hydrogen peroxide water mixture was 1 (sulfuric acid):1 (hydrogen peroxide water):1 (ultrapure water). In the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture (S31), the treatment time was 30 minutes, and the sulfuric acid-hydrogen peroxide water mixture was at room temperature.
Next, the step of cleaning with the ammonia-hydrogen peroxide water mixture (S32) was performed. The volume ratio among the aqueous ammonia solution, the hydrogen peroxide water, and the ultrapure water contained in the ammonia-hydrogen peroxide water mixture was 1 (aqueous ammonia solution):1 (hydrogen peroxide water):10 (ultrapure water). In the step of cleaning with the ammonia-hydrogen peroxide water mixture (S32), the treatment time was 30 minutes, and the ammonia-hydrogen peroxide water mixture was at room temperature.
Next, the step of cleaning with the aqua regia (S33) was performed. The volume ratio among the hydrochloric acid, the nitric acid, and the ultrapure water contained in the aqua regia was 3 (hydrochloric acid):1 (nitric acid):0 (ultrapure water). In the step of cleaning with the aqua regia (S33), the treatment time was 30 minutes, and the aqua regia was at room temperature.
Next, the step of cleaning with the hydrochloric acid-hydrogen peroxide water mixture (S34) was performed. The volume ratio among the hydrochloric acid, the hydrogen peroxide water, and the ultrapure water contained in the hydrochloric acid-hydrogen peroxide water mixture was 1 (hydrochloric acid):1 (hydrogen peroxide water):10 (ultrapure water). In the step of cleaning with the hydrochloric acid-hydrogen peroxide water mixture (S34), the treatment time was 30 minutes, and the aqua regia was at room temperature.
Next, the step of cleaning with the hydrofluoric acid (S35) was performed. The hydrofluoric acid in a mixed solution prepared by mixing the hydrofluoric acid and ultrapure water had a concentration of 30%. In the step of cleaning with the hydrofluoric acid (S35), the treatment time was 30 minutes, and the hydrofluoric acid was at room temperature. That is, in the cleaning step (S30) for each of samples 1 to 3, silicon carbide substrate 10 during cleaning was set to have a temperature of less than or equal to 40° C. This cleaning step is entirely performed at room temperature, due to the following reason. Since silicon carbide is chemically inert, it takes a long time to oxidize its surface and perform lift-off. In conventional cleaning such as so-called RCA cleaning, a sulfuric acid-hydrogen peroxide water mixture and a hydrochloric acid-hydrogen peroxide water mixture at a high temperature are used. However, when a sulfuric acid-hydrogen peroxide water mixture and a hydrochloric acid-hydrogen peroxide water mixture at a high temperature are used to clean silicon carbide, the sulfuric acid-hydrogen peroxide water mixture and the hydrochloric acid-hydrogen peroxide water mixture evaporate during cleaning treatment, and thus the cleaning effect is reduced. Accordingly, silicon carbide is preferably cleaned at room temperature.
(Measurement Method)
For each of samples 1 to 3, concentrations of metals existing in main surface 10A were measured. For sample 1, concentrations of vanadium (V), tungsten (W), molybdenum (Mo), platinum (Pt), nickel (Ni), titanium (Ti), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), aluminum (Al), sodium (Na), calcium (Ca), potassium (K), and tin (Sn) were measured. For samples 2 and 3, concentrations of vanadium (V) and zinc (Zn) were measured. The concentrations of the metals were measured by ICP-MS. Tables 2 and 3 show measurement results of the concentrations of the metals in main surface 10A of sample 1. Table 2 shows measurement results of the concentrations of metal catalysts existing in main surface 10A.
TABLE 2
[×109 atoms/cm2]
V W Mo Pt Ni Ti Cr
Sample 1 28 12 7 60 0.2 110 0.1
As shown in Table 2, for each of vanadium (V), tungsten (W), molybdenum (Mo), platinum (Pt), nickel (Ni), titanium (Ti), and chromium (Cr), the metal concentration indicates a value which is less than or equal to 1.0×1012 atoms/cm2, in main surface 10A of sample 1. The concentrations of vanadium (V) existing in main surface 10A of sample 2 and main surface 10A of sample 3 were 72×109 atoms/cm2 and 16×109 atoms/cm2, respectively.
Table 3 shows measurement results of the concentrations of metals existing in main surface 10A other than the metal catalysts. It should be noted that “ND” in Table 3 indicates that the concentration was undetectable because it was lower than a detection lower limit value (1×107 atoms/cm2).
TABLE 3
[×109 atoms/cm2]
Fe Cu Zn Al Na Ca K Sn
Sample 1 1.1 0.9 23 0.3 0.2 8 ND ND
As shown in Table 3, iron (Fe), copper (Cu), zinc (Zn), aluminum (Al), sodium (Na), calcium (Ca), potassium (K), and tin (Sn) were confirmed as the metals other than the metal catalysts, in main surface 10A of sample 1. However, it was confirmed that these metals in main surface 10A of sample 1 each had a concentration lower than 1×1011 atoms/cm2. The concentrations of zinc (Zn) existing in main surface 10A of sample 2 and main surface 10A of sample 3 were 16×109 atoms/cm2 and 21×109 atoms/cm2, respectively.
It should be understood that the embodiment disclosed herein is illustrative and non-restrictive in every respect. The scope of the present invention is defined by the scope of the claims, rather than the embodiment described above, and is intended to include any modifications within the scope and meaning equivalent to the scope of the claims.
REFERENCE SIGNS LIST
10: silicon carbide substrate; 10A: main surface; 11A: main surface; 20: epitaxial layer; 30: metal impurity; 100: polishing apparatus; 101: substrate holding portion; 102: polishing cloth; 104: turn table portion; 106: shaft; 108: polishing agent supplying portion; 110: polishing agent; 120: cleaning apparatus; 122: cleaning treatment tank; 124: pump; 126: filter; 128: heater.

Claims (14)

The invention claimed is:
1. A silicon carbide substrate having a main surface,
the main surface having a surface roughness (Ra) of less than or equal to 0.1 nm, and
vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium each having a concentration of less than or equal to 1.0×1012 atoms/cm2 in the main surface,
wherein vanadium has a concentration of more than or equal to 1.0×106 atoms/cm2 in the main surface.
2. The silicon carbide substrate according to claim 1, wherein vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium each have a concentration of less than or equal to 2.0×1011 atoms/cm2 in the main surface.
3. The silicon carbide substrate according to claim 1, wherein potassium, sodium, calcium, iron, copper, aluminum, and tin each have a concentration of less than or equal to 1.0×1010 atoms/cm2 in the main surface.
4. The silicon carbide substrate according to claim 1, having a diameter of more than or equal to 100 mm.
5. A method for manufacturing a silicon carbide substrate, comprising steps of:
preparing a silicon carbide substrate having a main surface;
polishing the main surface of the silicon carbide substrate using a polishing agent containing a metal catalyst; and
cleaning the silicon carbide substrate after the step of polishing,
the step of cleaning including a step of cleaning the silicon carbide substrate with aqua regia,
wherein
the step of cleaning further includes steps of:
cleaning the silicon carbide substrate with a sulfuric acid-hydrogen peroxide water mixture;
cleaning the silicon carbide substrate with an ammonia-hydrogen peroxide water mixture after the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture, the step of cleaning with the aqua regia being performed after the step of cleaning with the ammonia-hydrogen peroxide water mixture;
cleaning the silicon carbide substrate with a hydrochloric acid-hydrogen peroxide water mixture after the step of cleaning with the aqua regia; and
cleaning the silicon carbide substrate with hydrofluoric acid after the step of cleaning with the hydrochloric acid-hydrogen peroxide water mixture.
6. The method for manufacturing the silicon carbide substrate according to claim 5, wherein, in the step of polishing, the polishing agent contains at least one metal element selected from the group consisting of vanadium, tungsten, molybdenum, platinum, nickel, titanium, zirconium, and chromium, as the metal catalyst.
7. The method for manufacturing the silicon carbide substrate according to claim 5, wherein a treatment time is set to more than or equal to 15 minutes in each of the steps of cleaning with the sulfuric acid-hydrogen peroxide water mixture, cleaning with the ammonia-hydrogen peroxide water mixture, cleaning with the aqua regia, cleaning with the hydrochloric acid-hydrogen peroxide water mixture, and cleaning with the hydrofluoric acid.
8. A method for manufacturing a silicon carbide substrate, comprising steps of:
preparing a silicon carbide substrate having a main surface;
polishing the main surface of the silicon carbide substrate using a polishing agent containing a metal catalyst; and
cleaning the silicon carbide substrate after the step of polishing,
the step of cleaning including a step of cleaning the silicon carbide substrate with aqua regia,
wherein the step of cleaning further includes a step of cleaning the silicon carbide substrate with an ammonia-hydrogen peroxide water mixture, the step of cleaning the silicon carbide substrate with the aqua regia being performed after the step of cleaning with the ammonia-hydrogen peroxide water mixture.
9. The method for manufacturing the silicon carbide substrate according to claim 8, wherein a treatment time is set to more than or equal to 15 minutes in each of the steps of cleaning with the ammonia-hydrogen peroxide water mixture and cleaning with the aqua regia.
10. A method for manufacturing a silicon carbide substrate, comprising steps of:
preparing a silicon carbide substrate having a main surface;
polishing the main surface of the silicon carbide substrate using a polishing agent containing a metal catalyst; and
cleaning the silicon carbide substrate after the step of polishing,
the step of cleaning including a step of cleaning the silicon carbide substrate with aqua regia, wherein
the step of cleaning further includes steps of:
cleaning the silicon carbide substrate with a sulfuric acid-hydrogen peroxide water mixture, the step of cleaning with the aqua regia being performed after the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture; and
cleaning the silicon carbide substrate with hydrofluoric acid after the step of cleaning with the aqua regia,
wherein a treatment time is set to more than or equal to 15 minutes in each of the steps of cleaning with the sulfuric acid-hydrogen peroxide water mixture, cleaning with the aqua regia, and cleaning with the hydrofluoric acid.
11. A method for manufacturing a silicon carbide substrate, comprising steps of:
preparing a silicon carbide substrate having a main surface;
polishing the main surface of the silicon carbide substrate using a polishing agent containing a metal catalyst; and
cleaning the silicon carbide substrate after the step of polishing,
the step of cleaning including a step of cleaning the silicon carbide substrate with aqua regia,
wherein, in the step of cleaning with the aqua regia, the aqua regia in a mixed solution prepared by mixing the aqua regia and ultrapure water has a volume concentration of more than or equal to 50% and less than or equal to 100%.
12. The method for manufacturing the silicon carbide substrate according to claim 5, wherein, in the step of cleaning with the sulfuric acid-hydrogen peroxide water mixture, a volume of sulfuric acid contained in the sulfuric acid-hydrogen peroxide water mixture is more than or equal to one time and less than or equal to five times a volume of ultrapure water contained in the sulfuric acid-hydrogen peroxide water mixture, and a volume of hydrogen peroxide water contained in the sulfuric acid-hydrogen peroxide water mixture is more than or equal to one time and less than or equal to three times the volume of the ultrapure water contained in the sulfuric acid-hydrogen peroxide water mixture.
13. The method for manufacturing the silicon carbide substrate according to claim 5, wherein, in the step of cleaning with the ammonia-hydrogen peroxide water mixture, a volume of an aqueous ammonia solution contained in the ammonia-hydrogen peroxide water mixture is more than or equal to one tenth and less than or equal to one time a volume of ultrapure water contained in the ammonia-hydrogen peroxide water mixture, and a volume of hydrogen peroxide water contained in the ammonia-hydrogen peroxide water mixture is more than or equal to one tenth and less than or equal to one time the volume of the ultrapure water contained in the ammonia-hydrogen peroxide water mixture.
14. A method for manufacturing a silicon carbide substrate, comprising steps of:
preparing a silicon carbide substrate having a main surface;
polishing the main surface of the silicon carbide substrate using a polishing agent containing a metal catalyst; and
cleaning the silicon carbide substrate after the step of polishing,
the step of cleaning including a step of cleaning the silicon carbide substrate with aqua regia,
wherein, in the step of cleaning, the silicon carbide substrate is set to have a temperature of less than or equal to 40° C.
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Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106536793B (en) * 2015-02-02 2019-04-05 富士电机株式会社 Manufacturing method of silicon carbide semiconductor device and silicon carbide semiconductor device
CN115386342B (en) 2017-09-29 2024-02-06 福吉米株式会社 Polishing composition
WO2020077849A1 (en) * 2018-10-16 2020-04-23 山东天岳先进材料科技有限公司 High-flatness, low-damage and large-diameter monocrystalline silicon carbide substrate, and manufacturing method therefor
CN109321980B (en) * 2018-10-16 2019-11-19 山东天岳先进材料科技有限公司 A kind of high-flatness, low damage major diameter single crystal silicon carbide substrates
CN109571154A (en) * 2018-12-28 2019-04-05 天津洙诺科技有限公司 A kind of polishing method of 4H silicon carbide wafer
US12071708B2 (en) * 2019-05-17 2024-08-27 Sumitomo Electric Industries, Ltd. Silicon carbide substrate
WO2020235205A1 (en) * 2019-05-17 2020-11-26 住友電気工業株式会社 Silicon carbide substrate
US11913135B2 (en) 2019-12-02 2024-02-27 Sumitomo Electric Industries, Ltd. Silicon carbide substrate and method of manufacturing silicon carbide substrate
KR102340307B1 (en) * 2020-04-09 2021-12-15 포항공과대학교 산학협력단 Forming ohmic contact on 4h-sic substrate semiconductor and manufacturing method thereof
KR102236398B1 (en) * 2020-09-22 2021-04-02 에스케이씨 주식회사 Cleaning method for wafer and wafer with reduced impurities
CN117855025A (en) * 2022-09-30 2024-04-09 比亚迪股份有限公司 Silicon carbide epitaxial wafer and preparation method thereof
CN115592555B (en) * 2022-10-11 2024-12-10 南方科技大学 A surface conditioner for silicon-based materials and its application in shaping and polishing

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11157989A (en) 1997-11-25 1999-06-15 Toyo Tanso Kk Susceptor for gas phase growth and its production
JP2004014536A (en) 2002-06-03 2004-01-15 Nec Electronics Corp Method for removing contaminants from semiconductor substrate
JP2008280207A (en) 2007-05-10 2008-11-20 Matsushita Electric Ind Co Ltd Method for manufacturing SiC single crystal substrate
JP2009194216A (en) 2008-02-15 2009-08-27 Hitachi Ltd Manufacturing method of semiconductor device
JP2010004073A (en) 2009-09-29 2010-01-07 Tadahiro Omi Silicon carbide product, manufacturing method thereof and silicon carbide product cleaning method
JP2011230959A (en) 2010-04-27 2011-11-17 Kazuto Yamauchi METHOD FOR GRAPHENE FILM DEPOSITION ON SiC SUBSTRATE AND SiC SUBSTRATE WITH GRAPHENE
WO2013011751A1 (en) 2011-07-20 2013-01-24 住友電気工業株式会社 Silicon carbide substrate, semiconductor device, method for producing silicon carbide substrate, and method for manufacturing semiconductor device
US20130256700A1 (en) * 2012-04-02 2013-10-03 Sumitomo Electric Industries, Ltd. Silicon carbide substrate, semiconductor device, and methods for manufacturing them
US20140220299A1 (en) * 2011-10-07 2014-08-07 Asahi Glass Company, Limited Single-crystal silicon-carbide substrate and polishing solution

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NZ542844A (en) * 2003-03-11 2008-11-28 Primet Prec Materials Inc Multi-carbide material manufacture and use
KR100612853B1 (en) * 2004-07-21 2006-08-14 삼성전자주식회사 Si-based material layer containing a silicide in the form of a wire and a method of manufacturing the same
US7514323B2 (en) * 2005-11-28 2009-04-07 International Business Machines Corporation Vertical SOI trench SONOS cell
DE102006011312B4 (en) 2006-03-11 2010-04-15 Fachhochschule Hildesheim/Holzminden/Göttingen - Körperschaft des öffentlichen Rechts - Apparatus for plasma treatment under atmospheric pressure
JP4552968B2 (en) * 2007-05-29 2010-09-29 住友電気工業株式会社 Compound semiconductor substrate polishing method, compound semiconductor substrate, compound semiconductor epi substrate manufacturing method, and compound semiconductor epi substrate
US8734661B2 (en) * 2007-10-15 2014-05-27 Ebara Corporation Flattening method and flattening apparatus
JP4887266B2 (en) * 2007-10-15 2012-02-29 株式会社荏原製作所 Flattening method
JP5267177B2 (en) * 2009-02-04 2013-08-21 日立金属株式会社 Method for manufacturing silicon carbide single crystal substrate
JP2011003769A (en) * 2009-06-19 2011-01-06 Panasonic Corp METHOD OF MANUFACTURING SiC SINGLE-CRYSTAL SUBSTRATE
WO2013073216A1 (en) * 2011-11-14 2013-05-23 住友電気工業株式会社 Silicon carbide substrate, semiconductor device and methods for producing same
CN104023889B (en) 2011-12-06 2017-04-12 国立大学法人大阪大学 Method for manufacturing solid oxide and device therefor
WO2014050831A1 (en) 2012-09-28 2014-04-03 Hoya株式会社 Method for manufacturing substrate with multilayer reflective film
JP2014210690A (en) * 2013-04-22 2014-11-13 住友電気工業株式会社 Method for manufacturing silicon carbide substrate

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11157989A (en) 1997-11-25 1999-06-15 Toyo Tanso Kk Susceptor for gas phase growth and its production
JP2004014536A (en) 2002-06-03 2004-01-15 Nec Electronics Corp Method for removing contaminants from semiconductor substrate
JP2008280207A (en) 2007-05-10 2008-11-20 Matsushita Electric Ind Co Ltd Method for manufacturing SiC single crystal substrate
JP2009194216A (en) 2008-02-15 2009-08-27 Hitachi Ltd Manufacturing method of semiconductor device
JP2010004073A (en) 2009-09-29 2010-01-07 Tadahiro Omi Silicon carbide product, manufacturing method thereof and silicon carbide product cleaning method
JP2011230959A (en) 2010-04-27 2011-11-17 Kazuto Yamauchi METHOD FOR GRAPHENE FILM DEPOSITION ON SiC SUBSTRATE AND SiC SUBSTRATE WITH GRAPHENE
WO2013011751A1 (en) 2011-07-20 2013-01-24 住友電気工業株式会社 Silicon carbide substrate, semiconductor device, method for producing silicon carbide substrate, and method for manufacturing semiconductor device
US20130020585A1 (en) * 2011-07-20 2013-01-24 Sumitomo Electric Industries, Ltd. Silicon carbide substrate, semiconductor device, and methods for manufacturing them
US20140220299A1 (en) * 2011-10-07 2014-08-07 Asahi Glass Company, Limited Single-crystal silicon-carbide substrate and polishing solution
US20130256700A1 (en) * 2012-04-02 2013-10-03 Sumitomo Electric Industries, Ltd. Silicon carbide substrate, semiconductor device, and methods for manufacturing them

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